A preprint uses the surviving oscillations of 30 hot subdwarfs to place upper limits on their magnetic fields. Strong fields would damp particular stellar pulsations. The inferred bounds vary widely between stars and depend on stellar structure and field geometry, offering a complementary probe rather than a direct magnetic detection.
An arXiv preprint examines 30 hot subdwarfs, using their pulsations to limit the strength of their magnetic fields. It uses asteroseismology, which studies stars through their oscillations. The researchers examined low-frequency gravity modes: oscillations that sufficiently strong magnetic fields are expected to damp. The continued observation of those modes constrains the strength of the fields under the adopted stellar and wave models.[1]
At the low end, the inferred limits are about 20 gauss; at the high end they reach 30 kilogauss. A star’s properties and the oscillation’s frequency strongly affect the magnetic threshold for suppression. The tightest individual result therefore applies to that star and its observed oscillations.[1]
The authors find that oscillation-based constraints can compete with, and sometimes surpass, traditional spectroscopy and measurements combining spectra with polarisation. The methods probe different aspects of stellar magnetism and can complement each other.[1]
The calculation primarily constrains the radial field component, so strong fields running mainly around the star remain possible. The wave approximation may also break down in the outer layers, and some oscillation energy might survive magnetic damping. These are model-dependent upper bounds, with no direct magnetic-field detection claimed.[1]
